1. Field of the Invention
The present invention generally relates to image processing and, more particularly, to an image processing apparatus that processes images for a printer, a control method therefor, and a computer-readable storage medium.
2. Description of the Related Art
There is widely used a printing apparatus (printer) that receives print data regarding a print content or a print format, creates (renders) a bitmap image to be actually output based on the print data, and prints the bitmap image on a recording medium such as paper.
Japanese Patent Application Laid-Open No. 11-198462 discusses a technology for dividing print data of one page into a plurality of bands, and preventing print overrunning based on time required for rendering the print data of each band and time required for printing when the print data of each band is printed on a recording medium to be output. The print overrunning means that when rendering and image formation are performed in parallel, the rendering is not in time for a start of printing (corresponding to a transfer start of bitmap data for forming an image), thus disabling normal print outputting.
The technology discussed in Japanese Patent Application Laid-Open No. 11-198462 stores, in order to prevent the print overrunning, the print data of the band where the rendering is not in time for the start of printing, in a temporary band memory temporarily added by rendering before the start of printing.
Print overrunning occurring in a printer that processes print data of a plurality of pages, and prints the data of the plurality of pages on a roll sheet (roll recording medium) will now be described.
Such a printer prints the data while conveying the roll sheet. Hence, when rendering is not in time for transfer of bitmap data, the roll sheet is wasted (blank sheets are continuously output), or time for stopping the roll sheet is necessary. In the stopping of the roll sheet, to prevent wasteful outputting of the roll sheet, the roll sheet is rewound to immediately before a normally printed page, and returning the roll sheet to a standby position to be ready for a next printing start. Thus, the printer that processes the roll sheet should preferably perform processing to prevent print overrunning, also between pages similar to that occurring between the bands discussed in Japanese Patent Application Laid-Open NO. 11-198462.
However, using the method discussed in Japanese Patent Application Laid-Open No. 11-198462 to prevent print overrunning between pages in the printer that prints data on the roll sheet results in low efficiency in use of the memory for storing the rendered bitmap.
Even in a case where a band requiring predetermined rendering time is included in a last page of a great many pages, the printer must continuously store previously rendered bitmap data to prevent print overrunning between pages. However, as timing of releasing the previously rendered bitmap data from the memory (timing of finishing printing) becomes later, a storage period of data in the memory becomes longer, resulting in low efficiency in use of the memory.
As apparent from the foregoing, when the method discussed in Japanese Patent Application Laid-Open No. 11-198462 is applied to the printer for the roll sheet, as the number of pages included in print data to be processed becomes larger, much more memory for storing the bitmap data (the temporary band memory) becomes necessary, causing a reduction of use efficiency.